1. Field of the Invention
The present invention relates to a silver-nickel composite material for electrical contacts and electrodes, particularly for spark plug electrodes.
2. Description of Related Art
A silver-nickel composite in the form of a silver nickel fiber composite for electrodes, and a method for its manufacture, is known from German Offenlegungsschrift 25 08 490. Another German reference, German Offenlegungsschrift 022 59 636, discloses a manufacturing process for silver-nickel fiber composites.
Furthermore, German Offenlegungsschrift 32 13 481 describes a process to form a composite consisting of two helically wound silver alloy layers where, subsequent to coiling, the composite is arranged in a tube and is then extruded or drawn into wire.
When such composite materials are used for electrical contacts and electrodes, and more specifically are used for spark plug electrodes, there is the risk that the nickel components surrounded by silver components, and particularly those nickel fibers incorporated into a silver matrix, are exposed to chemical corrosion due to the fact that silver is not impervious to oxygen. This is particularly true when such silver nickel composites are used to form spark plug electrodes which are exposed to such chemical corrosion in the combustion chamber, leading in turn, to a reduction of their service life and durability.
As the space in the engine compartment of vehicles has become more limited due to an increased use of electronic components and the use of coatings for environmental protection, maintenance in the engine area has become more costly. It is, therefore, very desirable to maximize the length of time before spark plugs or spark contacts must be changed. The same rationale applies to biogas and gas engines whose spark plugs should have a long service life while undergoing a high degree of stress; an objective thus far only achieved by the use of platinum spark plugs, or electrodes which incorporate platinum metals or platinum alloys.